Muffle furnace



July 16, 1963 H. L. SMITH, JR 3,097,831

MUFFLE FURNACE Filed Aug. 51, 1960 s'sheets-sneet 1 o? INVENTOR #0414@- L 5mm' di?.

Zani/Mw'ggm H. L. SMITH, JR

MUFFLE FURNACE July 16, 1963 6 Sheets-Sheet 2 Filed Aug. 51, 1960 COMBUSTlO/y Gnases INVENTOR :l1/Genes L Sur/Je 6 Sheets-Sheet 3 H. L. SMITH, JR

MUFFLE FURNACE 15x-:als:-

E w En One/waas Foe Exfmusr Gas y GAS B July 16, 1963 Filed Aug. 51. 1960 NVENTQR /once L. Sn/m Je.

MUFFLE FURNACE med Aug. 51. 1960 6 Sheets-Sheetl 4 INVENTOR /oace L S17/n1 d?.

ATTORNEYS.

July 16, 1963 H. 1 SMITH, JR

MUFFLE FURNACE 6 Sheets-Sheet 5 Filed Aug. 3l. 1960 BY MM? TToRNEYs H. L. SMITH, JR

MUFFLE FURNACE July 16, 1963 6 Sheets-SheerI 6 Filed Aug. 3l, 1960 INVENTOR /v Ace- L. ff/ru d.

United States Patent O 3,097,831 MUFFLE FURNACE Horace L. Smith, Jr., Richmond, Va., assignor, by mesne assignments, to Burlington Industries, Inc., Greensboro, N.C., a corporation of Delaware Filed Aug. 3,1, 1960, Ser. No. 53,192 3 Claims. (Cl. 263-3) This invention relates to mufe furnaces for thermal treatment of sheet material. More particularly it relates to such furnaces for use in the thermal desizing of a glass fabric web.

In the manufacture of glass fabric, the individual filaments are coated with an organic size and/or lubricant to enable formation' of yarn and weaving of the latter. However, it is necessary to remove this material following |formation of the fabric to enable coloring or finishing of the goods. Desizing is effected by burning or vaporizing the size, and in this connection, it is known to utilize a closed oven into which rolls of fabric are placed for many hours and the size vaporized. However, this" expedient is costly and slow. It has also been proposed to utilize a horizontal furnace through which the rfabric is continuously advanced in open width and the size burned therefrom, but to achieve increased desizing speeds to keep pace with other improvements in ,the -treatment of glass fabrics, the horizontal furnaces have been lengthened to the point where with the passage of time the furnace sags appreciably under its own Yweight through met-al fatigue. Thus, upright furnaces have been proposed, wherein the Ifabric moves in a vertical path.

It has recently been discovered that a cleaner and physically stronger fabric can beg'achieved by vaporizing the size from the fabric in open width as distinguished from actual burning thereof at or adjacent the fabric surface. The details of that novel desizing process are set forth in the appli-cation of Edwin L. Lotz, entitled YProcess for Desizing of Glass Fabric, Serial No. 53,034, led on August 31, 1960; now Patent No. 3,012,845, issued on December 12, 1961.

It is a purpose of this invention to provide a novel muffle furnace which may be used -to carry out the novel Lotz desizing process.

It will be appreciated by those familiar with the ther- .mal desizing of glass that where the heat is generated by the combustion of fuel it is important to prevent direct Contact between the fabric and the gas flame, for example, lest the fabric be damaged by partial fusion. It has also "been found that a chemically cleaner fabric can be 'obtained if the products of fuel combustion are prevented from contacting the glass being desized. Accordingly, continuous desizing is carried out in a muiiie furnace, and this invention is directed to an improved furnace of that type.

In accordance with the present invention, I provide a Vertical m-ufe comprising 'a lpartition which separates the vertical run` of the furnace from the heat generating means and combustion chambers. In its preferred embodiment, the furnace actually embodies a vertical run defined on two sides by such partitions be'hind each of which is a c-ombustion chamber. These partitions serve to protect a glass fabric, for example, from direct contact with the flame `and the contaminating products of combustion, while absorbing heat from the combustion chambers and radiating to the fabric. Means are provided for exhausting the products of combustion from the combustion chambers. Independent means are provided for removing the gaseous products formed by vaporization of the size from the fabric in the vertical run.

CFI

3,097,831 Patented July 16, 1963 rfhe provision of such a run, or vertical muffle zone, poses the very significant problem of easily replacing the structural elements constituting the partitions thereof, the need Ifor such replacement being inherent where temperatures of the order of 1000-1500 F. are utilized. In this connection, the -diiiiculty and extended down time attending renewal of brick furnace linings is well knovsm. Therefore, as a salient feature of the present invention, I contemplate the formation of the partitions dening the mufe zone of :a series of units, referred to herein as plates, suspended one from another with the uppermost unit or plate mounted at the upper end of the muffle zone. Because the partitions should be excellent radiators, and must possess appreciable tensile strength by reason of their suspension, the individual plates are preferably Iformed of metal. By reason of this novel construction, replace-ment of a part of all of the partition is a simple matter, it being necessary only to disconnect each plate from the plate immediately above it and to form the new partitions by suspending new plates one from the other.

As a further important feature of the present invention, I construct my furnace so that the material web being treated actually .passes through several vertically aligned heating stages or zones. Each stage is similarly equipped with combustion chambers, exhaust means for drawing off the products of combustion and exhaust means for drawing oif the vapors in the respective muille zones. It is thus possible accurately to maintain different temperature conditions in each stage as desired to achieve maximum effects upon the material while maintaining maximum physical strength, and at the same time properly crimping the `fabric: to improve the hand thereof.

There has thus been outlined rather broadly the more important features of the invention in order that the following detailed description may be fully understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention described hereinafter which form the subject of certain of the appended claims. Those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as `a basis -for the design of structures other than those speciiically shown and described for carrying out the several purposes of the invention. -It is important, therefore, that the claims be regarded as including such equivalent constructions as do not depart from the spirit an'd scope of the invention.

A specific embodiment of the invention 'has been chosen for purposes of illustration and description, and is shown in the accompanying drawings, wherein:

FIG. l is .a front elevational View of two similar three stage furnaces in accordance with the present invention arranged in tandem, and illustrating the path of web travel;

FIG. 2 is a rear elevational view of the furnaces of FIG. 1

FIG. 3 is tan elevational view taken along the line Zs--S` of FIG. l;

FIG. `4 is a fragmentary side elevational view of a portion of the furnace broken away to illustrate various features of the invention;

FIG. 5 is a sectional view taken along the line 5-5 of FIG. 4;

gFIG. 6 is an enlarged view of a portion of the furnace as shown in FIG. 5 and illustrating a fuel burner;

FIG. 7 is a sectional view taken along the line 7-7 of FIG. 5;

FIG. 8 is a sectional view taken along the line 8--8 of FIG. 5;

FIG. 9 is a vertical sectional view illustrating the arrangement of muffle plates in the furnace;

FIG. is a perspective view showing the manner of suspension of an uppermost mule plate;

FIG. 1l is a fragmentary perspective view illustrating details of suspension of the upper plate.

Referring now to the drawings in detail, and more particularly to FIGS. l and 2` thereof, a pair of similar vertical mule furnaces 10 and 11 are arranged in tandem through which a web 12 of fabric to be treated passes as indicated by the arrows in FIG. 1. It is to be understood that one such furnace rn asuyflice and constitutes the present invention. In view of the similarity of the furnaces, a detailed description of one only will suce.

As shown in FIGS. 1 and 2, the furnace is provided at the bottom and top with suitable web feeding and guiding means indicated schematically at 14 and 15, respectively. Damper means are provided at the lower end of the furnace to permit control of a draft through the muilie zone. These damper means may, for example, comprise butterfly plates 13a and 13b operable by any convenient means (not shown).

Referring .to FIGS. 3, 4 and 5, the furnace actually comprises a housing 10 in three stages designated 16a, 10b, and 16C disposed in vertical alignment, each having refractory walls 16 formed of re brick, for example, which may in turn be lprovided with suitable exterior metal plates 17. Each stage is supported between corresponding pairs of arches 19a, 19h, 20a, Ztib and 21a, 2lb, respectively, and each of these arches is carried at its ends by structural members 22 and 24 which take the horizontal tand vertical components of the load respectively. These members 22 and `24 supporting each stage are in turn supported by suitable framing (not shown) so that each stage of the furnace is independent of the others as respects its Weight and expansion and contraction. Thus, as many stages as are necessary may be vertically arranged. Expansion joints are provided in each stage, as indicated at 23 in FIG. 4.

Each stage includes a pair of combustion chambers 25 separated by a central, vertical fabric run 26. In the outer wall of each of the combustion chambers 25 are mounted `a plurality of burners 27, each joined to manifolds 27a carrying a combustible mixture of fluid fuel and air, for example. As shown schematically in FIGS. 3 and 4, the fuel burners are preferably arranged in alternate spaced rows of three and four each to assure uniform heating throughout the chambers. Each burner may of course be equipped With a control valve 29 for regulating flow therethrough. Sight openings 36 and thermo-couple receptacles 31 may be located at convenient points in the Walls of each stage, as illustrated in FIGS. 3 and 4.

The fabric run 26 is actually a muflle zone disposed between the combustion chambers 25. As stated above, the walls of the muie zone or run 26 serves to protect the fabric web 12 from direct contact with the burner flames @and from the products of fuel combustion. As shown in FIGS. 5, 7 and 8, the muffle or run 26 is defined on two sides by the refractory walls of the furnace and on its other two sides by a series of novel muflle plates 32 assembled in a manner to be described hereinafter.

Referring now to FIGS. 1, 3 and 8, it will be seen that duct means are provided for drawing off the products of fuel combustion from combustion chambers 25. Thus, at the top` of each stage and on each side of the furnace, exhaust passages 34 are provided for each combustion chamber, and these passages extend Ithrough the furnace wall 16 which forms a part of the respective combustion chamber. Suitable exhaust ducts 35 fit into these passages and conduct the produc-ts of combustion to flue manifolds 36, one manifold serving the combustion chambers on each side of Ithe furnace, and merging into a main flue 37 near the top of the furnace (FIGS. 1 and 2). It will be seen that except for the exhaust, each combustion chamber is completely enclosed.

Turning now to FIGS. 2, 3 and 7, duct means are provided for drawing off vaporized size at selected points along the fabric run. These duct means are in addition to and separate from those already described in connection with the products of fuel combustion, and comprise exhaust 39 fitted into opposed, lateral passages 40, one at each side of the run 26 at the top of each stage. The ducts 39 at each side of the furnace are connected to vertical flue manifolds `41 (FIGS. 2 and 3) which discharge the vaporized size at ia Suitable location.

With the foregoing arrangement, it will be seen that the combustion gas and vapor-ized size exhaust systems are completely independent, and there is no possibility of flame reaching the web 12. Furthermore, a major portion of the size vaporized from the fabric in each stage is quickly removed from the vicinity of the fabric in that stage, which assures more thorough cleaning of the material.

It has been stated that the mule plates must present radiating surfaces and at the same time be resistant to the destructive effects of prolonged elevated temperature. For these reasons, I prefer to form the plates of one of the heat resistant steels, Inconel or Incaloy, for example. While ceramics might be employed, the aforementioned metals are preferred because they have a longer life and are not fragile.

As shown in FIGS. 9 to 11, the plates 32 which comprise the Inutile are elongate, fiat members with their up per and lower marginal regions turned back on opposite sides to form oppositely directed upper and lower hooks 42 and 44, respectively, whereby the plates may be suspended one from another as shown in FIGS. 5 and 9. The plates are reinforced in the regions of the hooks by spaced reinforcing webs 45 which may be welded in place. It will be noted that at least two of these reinforcing webs 45a at the top of the plates and preferably near each end thereof are somewhat larger than the others and are each formed with an opening 46 for a purpose described later.

As shown in FIGS. 5 and 9 to 11, the opposed upper plates in each stage engage a support 47 which may be in the form of a channel member set above the upper arch in its respective stage and having an upturned ange 49 for receiving the upper hook 42 of the top muffle plate. The support 47 is preferably formed of metal and its flange 49 is preferably reinforced by a secondary flange 5t) spaced therefrom and welded to the surface of the support, as are rigidifying members 51. The upper hook 42 of the upper muffle plate is recessed as to 52 to receive and engage members 51. Thus, the weight load of the mufiie plates of each stage is taken by the upper supporting arch and structural support members for that stage only.

Referring now to FIGS. 7 and 8, it will be seen that the mufe plates 32 are somewhat Wider than the inner transverse dimension of the furnace, and the opposed furnace walls at the side edges of the muflle plates are recessed as at 54 to receive the vertical marginal region of the plates. These recesses 54 are of such ydepth relative to the Width of the plates as to enable the plates to be cocked vertically, as shown in `broken lines in FIG. 4, and removed from the recesses at any level in the furnace.

From the foregoing description, it will be seen that when it becomes necessary to change the plates 32, the same may be accomplished merely by lowering a man or a scaffold into the muie to unhook the lower muie plate from the one above it, cock it, and remove it from the recesses 54, and hook it by one of the openings 46 in several of the reinforcing webs to lines 60 (FIG. 4) for withdrawal from above.

It will also be seen that I contribute by my invention a furnace in which each stage is a complete unit in itself, both structurally and operationally, so that different conditions may be maintained in each stage.

I claim:

1. In a furnace of the class described, a housing, means dividing said housing into a plurality of zones vertically disposed relatively to one another, said housing having vertical recesses in opposed side walls thereof in each of said zones, means for advancing a material web to be treated vertically through said zones, spaced partitions in each zone deiining a vertical muie run for said advancing material web, heat generating means positioned in each zone between said housing and each of said spaced partitions, said partitions each comprising a plurality of plates formed with cooperating means whereby each such plate supports the next adjacent lower plate, said cooperating means permitting separation of adjacent plates by vertical movement of the lower plate to be removed relatively to the next adjacent upper plate, said plates extending transversely of their respective zones and into said vertical recesses in the opposed housing side walls thus shielding the material from the atmosphere in the vicinity of the heat generating means, said plates being so dimensioned relatively to the w-idth of the respective zones and the depth of the recesses as to enable said plates to be cocked in a vertical plane and then removed from said recesses and said housing, said partitions absorbing heat generated by said heat generating means and radiating same to said material as it is advanced through said heating zones, exhaust means communicating with each zone of said run, and means for exhausting the products of combustion produced by said heat generating means in the respective zones.

2. ln a furnace of the class described, a housing having vertical recesses in opposed side walls thereof, means for advancing a material web to be treated vertically through said housing, heat generating means for raising the temperature within said housing to a desired level, a series of heat radiating plates having mutually cooperating means at the upper and lower edges thereof rendering adjacent plates removably dependent one from another and separable by vertical movement of a lower plate relative to the next upper adjacent plate, said plates when assembled forming a vertical partition in said housing and separating said advancing material from said heat generating means, said plates extending across said housing and into said vertical recesses and being so dimensioned relatively to the width of said furnace and the depth of said recesses as to enable said plates to be cocked in a vertical plane and removed from said recesses.

3. In a furnace of the class described, a housing, means dividing said housing into a plurality of zones vertically disposed relatively to one another, said housing having vertical recesses in opposed side walls thereof in each of said zones, means for advancing a material web to be treated vertically through said zones, spaced partitions in each zone deiining a vertical muflle run for said advancing material web, heat generating means positioned in each `zone between said housing and each of said spaced partitions, said partitions each comprising a plurality of plates formed with cooperating means whereby each such plate supports the next adjacent lower plate, said cooperating means permitting separation of adjacent plates by vertical movement of the lower plate to be removed relatively to the next adjacent upper plate, said plates extending transversely of their respective zones and into said vertical recesses in the opposed housing side walls thus shielding the material from the atmosphere in the vicinity of the heat generating means, said plates being so dimensioned relatively to the Width of the respective zones and the depth of the recesses as to enable said plates to be cocked in a vertical plane and then removed from said recesses and said housing, said partitions absorbing heat generated by said heat generating means and radiating same to said material as it is advanced through said heating zones, exhaust means communicating with each zone of said run at the upper region thereof and exhausting vaporized products from said run at each side of said material, and means independent of said exhaust means for exhausting the products of combustion produced by said heat generating means in the respective zones.

References Cited in the file of this patent UNITED STATES PATENTS 154,843 Colby Sept. 8, 1874 1,947,546 Reading Feb. 20, 1934 1,991,016 Fahrenwald Feb. l2, 1935 2,067,085 Hawke Jan. 5, 1937 2,156,008 Bowland Apr. `25, 1939 3,002,733 Barnes Oct. 3, 1961 FOREIGN PATENTS 446,957 Germany Feb. 10, 1920 

2. IN A FURNACE OF THE CLASS DESCRIBED, A HOUSING HAVING VERTICAL RECESSES IN OPPOSED SIDE WALLS THEREOF, MEANS FOR ADVANCING A MATERIAL WEB TO BE TREATED VERTICALLY THROUGH SAID HOUSING, HEAT GENERATING MEANS FOR RAISING THE TEMPERATURE WITHIN SAID HOUSING TO A DESIRED LEVEL, A SERIES OF HEAT RADIATING PLATES HAVING MUTUALLY COOPERATING MEANS AT THE UPPER AND LOWER EDGES THEREOF RENDERING ADJACENT PLATES REMOVABLY DEPENDENT ONE FROM ANOTHER AND SEPARABLE BY VERTICAL MOVEMENT OF A LOWER PLATE RELATIVE TO THE NEXT UPPER ADJACENT PLATE, SAID PLATES WHEN ASSEMBLED FORMING A VERTICAL PARTITION IN SAID HOUSING AND SEPARATING SAID ADVANCING MATERIAL FROM SAID HEAT GENERATING MEANS, SAID PLATES EXTENDING ACROSS SAID HOUS- 